Method for continuously grinding a drill tip end into a normal shape and into a split point

ABSTRACT

The specification discloses a novel method for continuously grinding a drill tip end into a normal shape and into a split point form, without removing and replacing the drill between the normal shape grinding procedure and the split point grinding procedure. A drill to be ground is first ground at its tip end portion into a normal shape, and subsequently but continuously to the preceding procedure the drill tip end is ground into a split point, whereby the drill can be ground in two ways in a single step of process. This means a great advantage over the prior art in speed of the processing and quality of the resultant product.

Mataichi Saito No. 13-3 6-chorne Chuo, Ota-ku, Tokyo-to, Japan [21] Appl. No. 721,683

Apr. 16, 1968 [45] Patented May 25, 1971 Japan 42/29150 DRILL TIP END INTO A NORMAL SHAPE AND INTO A SPLIT POINT 1 Claim, 11 Drawing Figs.

United States Patent [72] Inventor [22] Filed [32] Priority May 10, 1967 [5 4] METHOD FOR CONTINUOUSLY GRINDING A ground at its tip end portion into a normal shape, and subsequently but continuously to the preceding procedure the drill tip end is ground into a split point, whereby the drill can be ground in two ways in a single step of process. This means a great advantage over the prior art in speed of the processing and quality of the resultant product.

PATENTEU HAYZSIHH 3579.924

SHEETZUFS UMM 39mm SHEET 3 [IF 5 PATENTEU NAYZS I97! PATENTED W25 197i SHEET t [If 5 INVENTOR MATAI CHI SAITO ATTORNEYS PATENTED mzswn 3579.924

sum 5 ur 5 INVENTOR MATAICHI SATO ATTORNEYS METHOD FOR CONTINUOUSLY GRINDING A DRILL TIP END INTO A NORMAL SHAPE AND INTO A SPLIT POINT BACKGROUND OF THE INVENTION This invention relates to a method for grinding drills, and more particularly to a method and an apparatus for continue ously grinding the tip end portion of drills into a normal shape and into a split point form.

Generally drills are ground by providing a suitable cutting relief angle thereto and very often drills so groundare directly In this method, however, the drills were subjected to two separate procedures, that is, the normal .tip end grinding as the first step and then the split point grinding as the second step, with the removal and replacement of the-drills intervening between these two separate steps. Thus, this known method could not provide the split point grinding of drills in a single step of process.

SUMMARY OF THE INVENTION In view of the described drawback existing in the known grinding method, the present invention provides a novel method for continuously grinding the tip end of drills into a normal shape and into split point in a single process without the removal and replacement of the drills intervening therebetween.

According to themain feature of the present invention, a drill to be ground is first ground atits tipend into a normal shape, and thereafter, without being removed from. and replaced onto the machine, it is continuously subjected to the split point grinding whereby the drill tip end can be ground in two ways in a single step process. To this end, the'drill to be:

ground is rotated about the mounting axis thereof with respect to the grinding surface of a grind stone, swiveled rightwardly and leftwardly about the vertical axis passing the tip angle or angular portion of tthe drill, and a mechanism adapted to create said two types of motion is swiveled about the axis thereof perpendicular to the machine frame to which the mechanism is mounted.

The invention will now be described more fully with reference to a preferred embodiment thereof shown in the accompanying drawings, in which;

FIG. 1 is a partly cross-sectional side view showing a preferred example of apparatus embodying the present invention;

FIGS. 2 and 3 are sectional views taken along lines II-ll and III-Ill of FIG. 1, respectively;

FIG. 4 is a view illustrating the relative position between the FIG. 8 is a plan view illustrating one motion of the drill tipin accordance with the present invention;

FIG. 9 is a plan view illustrating another motion of the drill tip in accordance with the present invention;

FIG. 10 is a plan view illustrating the areas ground in accordance with the present inventionyand,

FIG. 11 is an illustration of the cam sequence providing the motion of FIG. 9.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now tothe drawings, agrind stone 1 is shown as having its upper and side surfaces precisely dressed with a diamond tool to which the present invention does not. relate particularly. The grind stone 1 inaccord with the tip angle of a drill I which is to be ground.

According tothe present invention, the drill 2.is given the following three types of motion so as-to effect the intended, grinding.

l. Rotating motion about the axis A-A (FIG. 1) of the drill 2 (this typeof motion is-hereinafter referred to as a first motion).

2. Rightward and leftward swivel motion about the vertical axis B-B (FIG. 1) passing thetip angle or angular portion of the drill 2 .(this type of motion ishereinafter. referred to as a second motion).

3. Swivel motion about the axisC-C (FIG. 1) perpendicular. and lateral to the machine frame to which the apparatus of the present invention is mounted for back and forth swivel motion (this type of motion is hereinafter referred to as a third motion).

Referring nowparticularly to FIGS. 1 through 3, upper and lower worms 3 and 4 mounted on a common shafta are rotated by a motor (not shown). The upper worm 3 engages a worm wheel 5 to transfer its rotation to the latter, which in turn provides the first motion for the drill retained centrally of said worm wheel 5;

The lower wonn 4 also engages another worm wheel 6 to thereby impart a rotating motion to a shaft b which is mounted along the center axis D-D of the worm wheel 6. Cams 7 and 8' are secured to said shaft'b.

In this arrangement, the upper worm 3 is threaded in single helix, the-lower worm 4 isthreaded in double helix, and the worm wheels 5 and 6 have the samenumber of teeth, whereby the shaft'b on the axis D-D effects two rotations per rotation of the mechanism holding the drill 2 so that, during the time the'drill 2 makes one rotation, the cams 7 and 8m the shaft b and a cam 9, which is loosely mounted on a shaft 0 on the axis B-Bito be rotated through a bevel gear e, effect two rotations respectively.

The drill 2 has two. grooves formed thereon, and two right and left cutting edges disposed symmetrically. One of the cutting edges of the drill. 2 is ground during the time when the shaftb and associated cams 7, 8 and 9 effect one rotation, and the other cutting edge of the drill is ground during the time when said ,three'cams make further one rotation, and thus it will be appreciated that a drill 2. is ground with two rotations of the shaft b.

Provision. is made of a coil spring l0 having one end thereof fixed to the worm wheel 5 and the other end fixed to a casing 11 holding the drill 2,'in such a manner that said coil spring can be compressed peripherally thereof.

This normally ensuresthe constant rotation of the worm wheel. 5; but when the casing 11 is temporarily stopped, the rotation of theworm. wheel 5 is not transmitted to the drill 2, which in turn stops its own rotation. During this time the coil spring 10 remains compressed.

Provision is alsomade of a roller 12 which is adapted to engage the cam surface of the cam 7 by a lever 13 pivotally mounted on a shaft 16; the lever'l3 being swungalong the concave and convex cam surfaces as the cam7 is rotated.

The cam 9 is idly rotated on the shaft c throughthe bevel (gears d and e, and a roller f adapted to engage the concave and convex cam surface of the cam 9 is rotatably mounted to a machine frame not shown. 1

The machine frame supports the entire mechanism of the present invention for swivel motion about the axis C'c. The cam 9 is always urged into close contact withthe roller f by a spring not shown.

In FIGS. 2 and 3, said three cams 7, 8 and 9 are intheir respective grind-starting positions.

When starting the grinding, the drill 2 is rotated in the directionas shown by the arrow 2 with its tip end in contact with the side surface of the grind stone 1. In this case, since the cam 9 engaging the roller f is gradually reduced in radius, the distance between the center of the cam 9 and that of the roller f is also decreased so that the entire mechanism is forwardly swiveled about the axis C-C to bring the drill 2 into the grindstarting position in which the center thereof is flush with the upper surface of the grind stone 1, as seen in FIGS. 1 and 4. As the grinding progresses, the drill 2 is rotating rightwardly as viewed in FIG. 1 and at the same time the axis of the drill swivels downwardly about the axis C-C.

The operation heretofore described serves to grind the drill 2 at the portions as designated by the letter A in FIGS. 6 and 7. Simultaneously the axis of the drill 2 swivels downwardly about the axis C-C, that is, the drill effects the third motion referred to previously, whereby a relief angle a is provided in the portions A of the drill 2.

Subsequently, a little before the grinding of the portions A is completed, the roller 12 goes down into the valley of the cam 7 to cause the lever 13 to rotate about the shaft 16, so that a projecting arm 14 extending from the lever 13 compresses a spring 15 mounted around a shaft rod 18 supported by the projecting arm 14, the spring 15 extending between said projecting arm 14 and a lever arm 17 which is loosely fitted on a shaft 19 at the upper end of the shaft rod 18. The lever arm 17 has an upper end forming a pawl 17, and the lower or root end of the arm 17 is associated with a supporting shaft 20. Through the compression of the spring 15, the pawl 17' of the lever arm 17 is received into the groove 11' formed in the casing 11 holding the drill 2, and further, a drill chuck 21 is slightly rotated to bring the pawl end of the lever arm 17 into engagement with the bottom wall of the groove 11 so as to temporarily stop the rotation of the casing 11. As will be appreciated, the worm wheel is always rotating, but this rotation only serves to compress the spring alone, while it is prevented from being transmitted to the drill 2 to thereby suspend the first motion temporarily.

During the suspension of the first motion, the second motion takes place to efiect the split point grinding of the drill.

Provision is made of a roller 22 (FIG. 3) adapted to engage the cam 8 mounted on the shaft 17, said roller 22 being attached by means of a curved bracket 23 to the machine frame 23 which carries a bearing for the shaft 0 and the axis C-C.

A cylindrical head 24 to which the drill 2 is mounted on a mounting plate 26, together with a bearing 25 for the shaft b, and the mounting plate 26 also has bearings 27 and 28 attached thereto, so that all the parts mounted on the mounting plate 26 can swivel about the shaft 0 on the axis B-B. Thus the drill 2 can be provided with the second motion.

The stop of the first motion of the drill 2 immediately causes the projection of the armlike cam 8 to be brought into engagement with the roller 22, whereby all the parts mounted on the mounting plate 26 swivel to the right, as viewed in the drawings, about the shaft c.

This provides the drill 2 with the second motion, and therefore the tip end of the drill is ground by the side of the grind stone 1 so as to form the portions B as shown in FIGS. 6 and 7.

As soon as this operation is completed, the roller 22 quickly goes down into the valley'of the armlike cam 8 to thereby cause the drill 2 assuming the second motion to quickly turn to the left and return to its original position.

Immediately thereafter, the roller 12 rises to the raised portion of the cam 7 to cause the projecting am 14 to move in the clockwise direction, so that the pawl 17 of the lever arm 17 is withdrawn from the groove of the casing 11 holding the chuck (this groove is formed contiguously with the aforementioned groove 11). Thus, the casing 11 which has been prevented from rotating by the pawl 17 is now quickly rotated in the clockwise direction by the compressive force of the spring 1, whereby the positional relation between the worm wheel 5 and the casing 11 returns to that before the grinding has been started.

Means such as pawl 29 may be provided to lessen the shock which is caused by the casing 11 being quickly rotated by the force of the spring 10.

As clearly shown in FIG. 1, the grind stone 1 has a dishlike shape. It rotates about its own axis at a high speed. The upper edge of the shoulder portion of the grind stone lies in the verti cal axis 3-8. The drill 2 in its starting position takes a horizontal position as shown in fig. 1. In this position, the tip end of the drill contacts with the shoulder edge of the grind stone 1 on the vertical axis B-lB. As described above, the drill 2 is given three types of motion. The first motion of the drill is a rotating motion about its own axis A-A. This motion is in-' dicated by the arrow 2 on FIG. 1. This motion is caused by means of a worm 3 mounted on a driving shaft a and a worm wheel 5 engaging with worm 3 (FIG. 2). The driving shaft a is rotated by a motor (not shown).

The worm wheel 5 imparts a rotating motion via the spring coil 10 to the casing 11 firmly holding the drill 2. In this manner, the drill 2 together with casing 11 rotate about its own axis A-A. The worm wheel 5 is driven continuously by the driven shaft a. But, the first motion of the drill is temporarily stopped. After one-half rotation, as above-described, the first motion of the drill is stopped.

It is apparent that no grinding action results from merely the first motion alone. In order to effectively grind the drill tip end into a normal cutting shape (portion A), it is necessary to combine the first motion with the third motion of drill.

The third motion is a swivel motion about a horizontal axis C-C. This motion is indicated by the arrow 2 in FIG. 8. When the third motion is caused, the axis A-A of the drill is swung around the axis C-C in such a direction that the shank portion of the drill 2 is moved downward on a vertical plane perpendicular to the axis A-A at a point within the circumference of the grinding surface, as seen from FIG. 8. The entire mechanism as shown in FIGS. 1 through 3 is fixed on the machine frame and supported by it in such a manner that it may pivot around the horizontal axis C-C. In order to cause this third motion, provision is made of the cam 9 and the roller f. The cam surface of the cam 9 contacts with the outer surface of roller f (FIG. 3). Since the machine frame supporting the entire mechanism is under the action of a spring (not shown) to urge the cam 9 to always contact the stationary roller f, the entire mechanism is swiveled around the axis C-C, in accordance with the change in distance between the center of the cam 9 and that of the roller f.

The amount of the swivel movement of the axis A-A of the drill depends on the shape of the cam surface. The shape of the cam surface is so determined that the normal cutting edge (portion A) may be just prepared during the swivel movement caused by the cam 9.

In the first step of the grinding process according to the present invention, the first motion (2') and the third motion (2) are started at the same time. The second motion has not yet started at this step of the process.

As illustrated in FIG. 8, by the first and third motions of the drill, the portion A at the tip end of the drill is ground off so as to form the cutting edge portion A as shown in FIGS. 6 and 7.

FIG. 10 illustrates the various grinding actions effected on the drill 2. Firstly, the portion 0-0 of the drill tip is ground off by the grind stone 1. Secondly, the portion 0-0" is ground off.

As the drill 2 rotates around axis A-A and also swings around the axis C-C during this grinding step, a cutting edge portion A having a conical surface with conical angle a is formed. When the grinding action has proceeded from 0-0 to 0-0", the first motion (2) of the drill is temporarily stopped in the manner mentioned above and then the second motion of the drill is caused.

The second motion is a swivel motion about the vertical axis 8-8. This motion is indicated by the arrow 2" in FIG. 9 and is a horizontal motion around axis B-B intersecting the axis of the drill A-A at the point of contact of the tip of the drill with the grinding surface. The second motion is caused by means of the cam 8 and the cam follower (see FIG. 11). All of the elements including the drill holder mounted on the supporting plate 26 can be turned rigl t vard and leftward (backward) around the axis B-B. The cm 8 is rotatable about the axis D-D. The roller 22 is fixed on the machine frame 23 by means of a curved bracket 23' (FIG. 3). The cam 8 comprises an extremely projecting portion and a semicircular portion.

As described above, while the drill 2 makes a half revolution, the cam 8 executes one rotation. When the roller 22 comes into contact with the cam surface of the projecting portion of the cam 8, the second motion 2" is initiated and continues until the roller 22 has left the projecting portion and come into contact with the semicircular portion of the cam. When the second motion 2" is stopped, the first motion 2 is again started. The time during which one continuous movement of the drill in the sense of the second motion 2" continues, corresponds to the time which the drill 2 would take for one-fourth rotation about its own axis A-A (but during this time, the drill 2 actually does not rotate about its own axis AA for the reason mentioned above).

During the movement of the drill resulted from the combination of the second motion 2" with the above-mentioned third motion 2", the portion 0-0' of the tip (see FIG. 10) is ground off so as to form the cutting edge surface B (FIGS. 6 and 7). As explained above, the first motion 2 is stopped during this time.

Therefore, the ground portion B has an edge surface with an angle greater than the angle a of the portion A. in such a manner, one half of the drill tip periphery is ground. By repetition of the same operation, the remaining half portion thereof can be ground so that a split point is completely formed at the point of the drill.

From the above explanation, it will easily be seen that according to the present invention, the tip end of drill can be continuously ground into anormal shape and into split point in a single process without any interruption.

Although description has been made of a preferred embodiment of the present invention, it is to be understood that the scope of the invention is only limited by the appended claims.

lclaim:

l. A method for continuously grinding a drill tip end comprising rotating a grind stone having a grinding surface about the axis thereof; mounting a drill to be ground with the tip thereof on said grinding surface; rotating said drill about the axis thereof, the axis of said drill being perpendicular to the axis of said grinding stone; simultaneously swinging said axis of said drill downwardly in a vertical plane around an axis perpendicular to said axis of said drill at a point within the circumference of said grinding surface, whereby a first cutting surface having a first angle is formed on said drill tip end; stopping said rotation of said drill while maintaining said swinging and simultaneously swiveling said axis of said drill horizontally around a vertical axis intersecting said axis of said drill at the point of contact between said tip of said drill and said grinding surface, whereby a second cutting surface having a second angle greater than said first angle is formed on said drill tip end. 

1. A method for continuously Grinding a drill tip end comprising rotating a grind stone having a grinding surface about the axis thereof; mounting a drill to be ground with the tip thereof on said grinding surface; rotating said drill about the axis thereof, the axis of said drill being perpendicular to the axis of said grinding stone; simultaneously swinging said axis of said drill downwardly in a vertical plane around an axis perpendicular to said axis of said drill at a point within the circumference of said grinding surface, whereby a first cutting surface having a first angle is formed on said drill tip end; stopping said rotation of said drill while maintaining said swinging and simultaneously swiveling said axis of said drill horizontally around a vertical axis intersecting said axis of said drill at the point of contact between said tip of said drill and said grinding surface, whereby a second cutting surface having a second angle greater than said first angle is formed on said drill tip end. 